Parking meter



PARKING METER Filed Dec. 25, 1950 I 5 Sheets-Sheet 1 can! i, mar ll pm INVENTORS. DONALD a. GUMPERTZ ggssa c. ALEXANDER W 1.9 #2 ya Sept. 15, 1953 D. GUMPERTZ ETAL PARKING METER 5 SheetsSheet 2 Filed Dec. 23, 1950 R 5 2 E mmm N MEN n V T NM %7 c V L L v Mm 5 wRw/vy Sept. 15, 1953 D. G. GUMPERTZ ETAL 2,652,551

PARKING METER Filed Dec. 23, 1950 s Sheets-Sheet s INVENTORS. DONALD 6. GUMPERTZ. BIEUSSEL c. ALEXANDER 7 l VS.

Sept. 15, 1953 D. e. GUMPERTZ ETAL PARKING METER 5 Sheets-Sheet 4 Filed Dec. 25, 1950 IN VEN TO$ DOAMLD 6. GUMPERT RUSSEL C. ALEXANDER BY ATTORNE VS.

P 1953 D. G. GUMPERTZ ET AL 2,652,551

PARKING METER Filed D90. 23, 1950 5 Sheets-Sheet 5 SENS/N6 MAGNET/C To 7 r PARK/N6 u/v/r. AMPLIFIER. RELAY METER 22 i z H A.C. zz/

DIRECT POWER CURRE N 7', INPUT BIAS INVENTORS. DONALD G. GUMPERTZ. BfUSSEL C. ALEXANDER ATTORNEYS.

Patented Sept. 15, 1953 :PARKJNG METER jihna iG- Gni iipe 'lt hilcl wn d,iah i fiu fsel"qAlexanderyLbng Beach, Calif assignors, by missile-assignments, to M & M Manufacturilig 'Gcifporation, -a corporation -"(if (Delhi-ado .Anbueation December 23, 1950,-SerialNo. 203,533

:1 4Claims. '1

This inven-tion relates .to ipa'rkin'g meters Land .has ,Lpart'icular Lreference lt'o a resetting ,mechanismffor returningmhejtime indicator or 1(- .ing meter etc :a .zer'o reading whenever .a H vehicle is moved out of the parking area 'associ eatediwithsuch parking meter.

vAltl'ioug h"numerous parking fmeters havebeen devised and used {in the {past the Lmajority of these devices have the .Ydisadvantage that they do notr return rto .,a ze r.o- 'reaamg until the (expira- -tion ot a predetermined time interval. flfhu s, the-operator of awhiclemay deposita coin in such meter for perhaps ,a :one-hour parking pe- .:riod,;:and use on ly aQsmall .fraction of that time, with the :result that other motoristsma'ydrive into the vacated stall. or-.parking.area-and use cthe .sbalance oflthe [timepn the meter without ithe mymenteof anym rkin .=As theuse-of sparking :meters is a ;means .pi both controlling marking "and rra-ising revenue for a.m ur, 1icipal1ty, it will be apparent that the revenue may hein- :.cr'ease,d tqonsiderably :if the i-parking meter ;may he :returned srto a i ze ro treading -,-immediately the parking stall is vacated, so thatft henext motorist iis icom-pelled to :Pay .-,the .usual parking .fee.

She-timing devices used unconventional park- .ing rmeters {are wusually driven lay ;a .clockiyork imechan-ism, i'the 'mainspring of which requ res periodic :winding. :In .0116 ty e-pf meter, artrangements are :made for periodic ,windings ot the clock maihspring bymoli-cemen or. other employeesrof "the amunicipality. cost of keepdng the marking; meters wound is :mate ria l, Tand aconsiderable increase yin the ;net revenue taken "by "the; parking. meter canaibe *real-izedzhy: the-'elim- '-}ination oftthe requirement for-winding the clock spring. I

iIn mother iitypes iOf parkin meters, the gmot'orists, npon qthe :deposit of a 1 coin, 1 are required irto :turn. a skey am handle in order .to ;move .jthe .tzim'e indicator 3150117118 .full sixty minutes paid. B'Ihisrkexmnhfifldlfi is-e rcnn e hessprine :of :the 20108 gas {to :at least partially wind the rsnringceachitime :the ;-handle is operated in the manneridescribed. While this arrangementelimiinates the:costef-.:emp1Q nsa -edto wind the isnaizkingzmetersgit. introduces a; further. disadvanttage which :resalts, f-romthev fact thatean apz precieblezzfractien ofiflr v s 0f autemobile s have tsixhstantial ly :no {mechanical sense, .an .d t

ing meters. Thesea motoristsmwhoMould quite likely b'e w Il'ing tmmereIy depositra iceinpin a slotor the pritfiilege of 'usingthe vacant spade, asueiiy drive to a 1 free :parking areapdrnarkmh i e cl s in a p ivate pa tki.ng

lotor garageratherthan attempt to unraveljth'e myster f the opera o .Q th parkin me Iihe successful and effective use of parking 5 jmeters for the control ,of parking andior the productionof revenue for amunicipality depends in large part upon the ,maintenance of a ;uni- ,formand. consistent policy oflciting. motorists ;for .such violations of .the parking ordinances .as leaving their vehicles parked a lon er time ,than the time paid ;for ,by the deposits of coins, or deliberately parking in a yacantstaII without depositing. coins to .pay for the parking privilege. The policing of an extensiveparking 'metertinstallation 'is an element of considerable cos'tin the .mainte'nanceof the system. Conventional parking meters employ .a red mechanical ,flag which. appears in-the window area of theparking meter whenever the ,parking .meter indicates a zero reading. In order to determine whether the parkingordinanceshavebeen violated, ;it is necessary for 'a policeman .to .patrol .the .entire "installation in order .to ,.dis'cover the individual violations. .{Since such patrolling is .a .time consuming .pro'cess, many violations remain undiscovered,

It is, .therefore, an obj ect of this invention .to 1prxgngide.a parking .meter .w'hich includes a resetting mechanism gm resetting .the time .in-

3 .dieator of ,the meter .to zero .whenever theassociated parking areais vacated.

It =is also an ohg'e ctof this invention to pro-- vide ,a parkingimeter. of .the. character .set forth in 313116 preceding paragraphs .in .which the re- 35 t in (mechanism employs an electronic apparatus-for sensing.electrically the absence or 'p resence ofwavehicle,in;the:parking area.

It is an additionalohject of this invention to provide a parking *metepof the character set Jorthherei-nbeforain which the electronic apparatus respondsto changes in themutualind-uctanc b ween t WO nduct nc m an :re- :sult ne fro th m v nec a n k d h f m the parking area.

.It is -,.ano..the geb c t i {in entio t a .vide;;a;parking eter.- of;the character set forth n h precedi-n m rae aph i w i -e e tronic apparatus:resn ndsa t chan e t wara tanc .1Q ana l ctr :Sur a aan v esul in from theqmovingiof aparked vehicle fro'mthe understandithe manner 'ofwpe atiq cofathe;,pa1?

tparkine :e e v It is a still further object of this invention "to nmvide ;.a par n .mete of t har ter d cri;be. h re n eforein wh h th ctron -t pstznaratus .n snend t cha s in th en atio Q) of the earths magnetic field and resulting from the moving of a parked vehicle from the parking area.

It is also an object of this invention to provide an apparatus of the character set forth in the preceding paragraph in which the changes in the orientation of the earths magnetic field are used to induce a control potential in an inductance coil.

It is also an object of this invention to provide a parking meter of the character set forth in the preceding paragraphs in which the electronic apparatus responds to changes in the inductance of an electrical circuit and resulting from the moving of a parked vehicle from the parking area.

It is an additional object of this invention to provide a parking meter of the character set forth in the preceding paragraph in which the changes in inductance produce corresponding changes in the frequency of an alternating current signal.

It is also an object of this invention to provide an apparatus of the character set forth in the preceding paragraphs in which the changes in inductance change the balance conditions in an inductance bridge circuit.

It is a still further object of this invention to provide an electronic parking meter apparatus of the character hereinbefore described in which changes in inductance are used to change the Q of a tuned circuit.

It is another object of this invention to pro vide a parking meter of the character set forth in the preceding paragraphs which includes a 1 spring winding mechanism operatively connected to the resetting mechanism for at least partially winding the clock spring of the parking meter timing device whenever the resetting mechanism is actuated.

It is also an object of this invention to provide a parking meter of the character set forth in the preceding paragraphs in which the electrical instrumentalities are arranged to be energized by local batteries, individually associated with the individual parking meters, and which includes means for periodically momentarily energizing the electronic apparatus to thereby materially extend the useful life of the batteries beyond the life to be expected were the apparatus energized continuously.

It is an additional object of this invention to provide a parking meter system using a plurality of individual parking meters, and in which each parking meter is electrically connected to a centrally located supervising station in such a way as to indicate at that center each violation of the parking ordinance.

It is another object of this invention to provide a parking meter system of the character set forth in the preceding paragraphs which includes a central totalizing system for indicating the total number of operations of all parking meters.

Other objects and advantages of this invention will be apparent from a consideration of the following specification, read in connection with the accompanying drawings, wherein:

Figure l is a perspective view partly in sec tion illustrating a typical parking meter installation employing the novel features of this invention;

Figure 2 is a diagrammatic view illustrating the construction of a parking meter and the resetting mechanism therefore and illustrating in block diagram form the control apparatus used for controlling the resetting mechanism, and illustrating further the manner of interconnecting each parking meter of a parking meter system with a violation indicator and a totalizer located at a central supervising station;

Figure 3 is a wiring diagram illustrating the electrical apparatus and connections employed in an electronic sensing apparatus responsive to changes in mutual inductance;

Figure 4 is a fragmentary perspective view illustrating an alternative method of installation of parking meters and showing a modified form of exciter device which may be used with the circuit shown in Figure 3;

Figure 5 is a diagram similar to Figure 3, but illustrating the construction of a sensing apparatus which is responsive to changes in the capacity of an electrical surface;

Figure 6 is a wiring diagram also similar to Figure 3, but illustrating a circuit which responds to changes in inductance to produce a change in the frequency of an alternating current;

Figure '7 is an electrical circuit similar to Figure 6, but illustrating the use of the change in inductance for changing the balance conditions in an inductance bridge;

Figure 8 is a wiring diagram illustrating the construction and mode of operation of a sensing apparatus which is responsive to a change in the orientation of the earths magnetic field, such change resulting from the movement of a vehicle into or out of the parking area associated with the parking meter;

Figure 9 is an electrical circuit similar to Figure 7, but illustrating the construction and operation of a sensing device in which a change of inductance is used to change the Q of a tuned circuit; and

Figure 10 is a block diagram illustrating the use of a magnetic amplifier in the sensing and control apparatus.

Referring to the drawings, there is illustrated in Figure 1 a more or less conventional parking meter installation. The parking meter proper, which is indicated generally by the reference character I0, is mounted upon a suitable standard or post H, set into the ground or cast into the concrete of which the sidewalk I2 is usually formed. The standard II is customarily positioned near the curb l3, and the surface M of the roadway proper is painted or otherwise marked with lines I5 and I6 to define a stall or parking area associated with the parking meter I0.

In accordance with the present invention, th support or standard II is made of pipe or tubing so as to accommodate a conduit I'I used to connect a sensing element indicated generally at I8 with sensing and control mechanism mounted in a suitable housing l9 secured to the standard I l and operatively connected with the mechanism of the parking meter II! in a manner to be described hereinafter. The hollow standard ll may also provide a connection with a conduit 20 which is used to interconnect all of the parking meters of a given system and for connecting such a plurality of parking meters to a centrally located supervisor station for purposes which will be made more apparent hereinafter.

As may be seen from Figures 1 and 2, the parking meter Ill comprises a housing 2| which is provided with a coin receiving aperture 22. Both vention contemplates the provision of a mechanism for momentarily energizing the sensing unit Hi and sensing unit amplifier 4| at regular periods. By this means, the life of the batteries is greatly extended because current is drawn from the batteries only during the short periods of momentary energization. The resetting mechanism will be actuated in the manner described at the time of the first momentary energization following the removal of the parked vehicle from the parking area.

The described intermittent energization of the sensing unit l8 and sensing unit amplifier 4| may be effected by means of a switch mechanism 53 which is mounted within the housing 2| of the parking meter head. The switch 53 is of the normally open type, and is positioned to be periodically actuated by a cam lobe 54 secured to or formed integrally with the driving half of the slip clutch 29. The cam lobe 54 engages one of the members of the switch 53 so as to close the switch during the fraction of each revolution of the clutch member 29 during which the cam lobe 54 engages the switch. If a twelve-to-one drive ratio is provided by the gears 21, 28, the cam lobe 54 will be rotated approximately once every twelve minutes. If it is desired to close the switch 53 at more frequent intervals, a higher drive ratio may be provided by the gears 21, 28; or alternatively, a plurality of cam lobes 54 may be spaced about the periphery of the clutch member 29.

The connection of the momentary switch 53 to the sensing unit amplifier is illustrated diagrammatically at 55 in Figure 2. The precise electrical circuitry employed in this connection is hereinafter described in detail with reference to Figure 5.

There is shown in Figure 3 the electrical circuits employed in a preferred form of the invention in which the sensing unit I8 is responsive to the changes in mutual inductance between two inductance coils produced by the moving of a vehicle into or out of the parking area. The sensing unit l8 in this form of the invention is preferably buried beneath the surface I4 of the roadway in the central portion of the parking area associated with the parking meter l0. While the sensing unit I8 is preferably buried beneath the surface of the roadway, the same may, if desired, be mounted upon the surface thereon, in which event the components of the sensing unit are made relatively thin and flat so as to reduce to the minimum the obstruction caused thereby.

In the form of the invention shown in Figure 3, the sensing unit I8 consists of two inductance coils, an exciter coil 66 and a pickup coil ill. The exciter coil 60 may comprise a substantial number of turns of suitably sized wire wound to a diameter of about six inches, and placed with its axis extended Vertically. Pickup coil BI is preferably formed as a multiple turn iron-cored inductance of small diameter and high impedance. In making the installation, the coil BI is adjusted as to orientation to a position providing substantially no coupling between the coils 60 and 6| when there is no vehicle in the parking area.

The exciter coil 60 is connected, as shown at '62, through a suitable fuse 63 to a source of alternating current power, represented by the terminals 64 and 65. This source of power is also connected, as shown at 66, to a power rectifier 61, the output of which is filtered as by a resistance 68 and condensers 69 and Ill to provide on a buss H a direct potential suitable'for use as a plate supply for the various vacuum tubes employed in the circuit to be described.

The pickup coil 6| is connected as indicated at 12 to the grid of a vacuum tube 13 which is connected in a conventional circuit with a second vacuum tube 14 to provide a two-stage resistancecoupled amplifier. The amplified output of the input signal appearing on the conductor 12 is applied as by a conductor 15 to a rectifier l6, and the rectified output is developed as a negative potential across a rectifier load resistance 11. This negative potential is applied as indicated at 18 to the grid of an output tube 19, the plate of which is connected as by means of conductors 8|) and 8| through the coil of the relay 43 to the output of the power supply rectifier 61. The alternating current operating potential applied at terminal 64 is conveyed, as by conductor 82, to a movable contact 83 of the relay 43. The normally open and normally closed stationary contacts of the relay 43 are connected by conductors 44 and 46, respectively, to the limit switches 45 and 41 in the manner hereinbefore described.

The operation of the circuit just described may best be understood by assuming a set of operating conditions and tracing the sequence of operations which results from a change in those conditions. Assuming that the parking stall is vacant, substantially no signal is induced in the pickup coil 6| because of the minimum coupling between the exciter coil 60 and the pickup coil 6|. The output of the amplifier 4| is therefore nearly zero, and the rectified voltage appearing across the rectifier load resistance H is of negligible value. The return end of this resistance is grounded, as shown, with the result that the grid of the output tube 19 is maintained substantially at ground potential. The cathode of that tube being grounded as shown, the tube draws a substantial plate current which energizes the relay 43 and closes the normally open contacts thereof so as to connect the supply conductor 82 to the conductor 44. AS- suming that the parking meter is in its zero position, the circuit is interrupted at the limit switch 45 which is open in the zero position of the parking meter timing device.

If it now be assumed that a motorist parks a vehicle in the parking area, the magnetic materials used in the construction of the motor vehicle provide a considerable coupling between the coils 60 and 6| so as to now cause a voltage to be induced in the coil El and applied as an input to the amplifier 4|. It has been found that the sensing unit arrangement described is substantially insensitive to small masses of metal, such as bolts, nuts, and such things which might normally be found on a roadway. However, the balance is upset sufficiently by the presence of a parked vehicle to produce a signal on the conductor 12 having a magnitude at least one hundred times as large as the signal appearing thereon when no vehicle is in'the parking space. This signal is amplified in the amplifier 4| and rectified by the rectifier 16 to apply a substantial negative potential to the grid of the output tube 19, the amplification of the amplifier 4| being selected to produce a negative voltage at the grid of the tube 19 of sufficient magnitude to bias the tube 19 substantially to cutoff. This reduces to a negligible value the current flowing in the coil of the relay 43, and causes the relay aaaass normally closed conrelaycontacts and. by way of conductor 46, limit switch 41' and conductor 18 to the annunciatcr panellil, anda indicate a violation of the parking ordinance- If, on. the other hand, the motorist removes vehicle from the parking. space. before. the expiration of. thetime. paid for, the zero coupling balance. between coils. an and. 6 I. is restored. causing the. signal. applied as. an. input. to. the ampliher Al to fall substantially to zero., The grid of the output tube 19 shifts correspondingly in the positive direction to cause the tube T9. to draw plate current and; energize. therelay 4.3.. This closes. the normally open contacts of the relay 43,. completing. a power circuit extending from. the. conductor 82,. through the relay contacts. and through. conductor 44. and normally closed. limit switch 45- to, energize. the resetting solenoid 3|. Energiza-tion in the. solenoid 3|. winds the clock spring and returns the time. indicating needle 35to-zerdposition at. which point. the limit switch 45 is. opened to open the circuit to the solenoid i r The; circuit. arrangement illustrated and. described with reference to Figure 3 may be used in a system. such as is shown. in Figure 4, cmplaying arr-alternative. construction of sensing. unit 18... The sensing unit. 1,8. which is to be used. with the system shown. in Figure 4,..will be understood to, include only the. pickup coil. 6 The. excitation may he provided. by a pair of. parallel conductors or buss bars 90, andv 91, either buried in. the street or secured. to. the surface thereof. The: outer ends of. the buss bars 90 and 91 are interconnected, astshown at. 92, and the. inner ends are connected, as. shown at. 93, to the. secondary winding. of a. low voltage. transformer 94, the; primarywi-nding oi which: connected,v as represented at 955-, to a, suitable. source of alter natingcurrent. power.

The conductors. 9,0 9.1., 9 2,. and'93- are. made of extremely-low resistance, and. the secondary voltdeveloped. by the. transformer 9.4 may be of the; order. of; a few volts so as to. cause a substantial. current to flow in the buss bars 90. and 9.1. without consuming an excessive amount of power. The interconnected buss bars 90 and 9;! thus n-stitute a. single'turn coil for developing excl-tin field: in. the same way as an exciting fieldyis; developed. by the exciter. coil 6.0. The pickup. coil. 54 or each-of the sensing units- 1-8 is so. adjusted. in its orientation as to bear a zero coupling relation. to: the single turncoil defined by the bussebarafillfi and 9 I; when there is no vehiole parked in the parking area associated with that; sens ng unit. Exceptfor. this; difierence. in themode; ofisupplyingi, the-exciting. field, the arrangement shownxin- Figure 4: will be; understood to; operate in. exactly the; same way as has. been. described in refierenceto-Figurea.

In Figure 5. there; is. shown a sensing unit and control apparatus operating to sense and determine-the presence or absence of a. vehicle in the associated: parking; area,v through a. change in the 7.5: vacuum tubes I02, [.M and H11 employ light,.

electrical capacitance of an electrical surface. In the. form illustrated in. Figure 5', they electrical surface may comprise an antenna Hill which is preferably mounted. on the curb near ther parking area so as to have its efiective capacity to ground vary in. accordance with whether a vehicle is parked in the parking area.

The antenna Hill is connected, as. shownat Ill-l, to the grid. of; a vacuum tube I02 which is connested in. a conventional self -oscillating circuit of the Hartley type- The output signal generated by the operation of the oscillatory circuit is taken from the cathode of tube ['02, and applied, as indicated at. 1.03,. to a rectifier I04 operating to develop across a load resistance Hi5, a. direct potential which is negative with respect to ground This negative potential is applied, as indicated at I06, to the grid of an output tube Ifl'l, in. the plate circuit of. which is connected the relay 43.

The apparatus is so adjusted as to make the oscillator [02' inoperative in the absence of a parked vehicle. This is accomplished through appropriate adjustment of the capacitance of the antenna. I00 and the-proper selection of grid condenser lllii and grid leak I09, used to connect thev grid of the tube I02 to atank circuit of the oscillator comprising a tank coil H0 and tank condenser I'H. With a tank condenser having a capacity of mmf. and a tank coil having an inductance of approximately 20 mh., it has been found that a grid leak resistance N9 of one megohm and a. grid condenser 10$ of 500' Inmf. produces the desired type of operation.

I-he removal of. a parked car from the parking area causes the. oscillator [02 to drop out. of operation, or at least to materially reduce the amplitude of the. output. The balance of the circuit operates in. exactly the same way as does the circuit illustrated and described with reference to Figure 3', the relay 43' being energized whenever the parking stall is vacant and being deenergized. whenever a vehicle is parked adjacent the sensing unit I8;

It will be understood that. the circuit shown in Figure 5 may be supplied with operating power from av commercial power source by using a power rectifier in the manner described with reference to, Figure. 3.. The circuit. is equally adapted, how'- ever, to. battery operation and as an illustration of. such arrangement. of the apparatus, battery power supplies have been illustrated and shown in Figure 5.. .Such a battery installation may include. a. plate battery H2, one terminal of which is grounded and the other terminal of which is suitably connected to the anodes of the vacuum tubes. H12 and MIT, as shown. A second battery LIL? for supplying. current to energize the filamerits. of. the vaccum tubes I02, I'M and 101 has one. terminal grounded. and the other terminal connected through the intermittently actuated momentary contact switch 53, and byway of conductors H4... H5, H5. and I I! to the filaments of the; individual vacuum tubes.

A. separate battery Il8 may be connected'in circuit with the contacts of the relay 43 for ener g-izin-g the. solenoid: 3.1L.

It will be seen. that the. periodically operated momentary contact switch 53 operates to close the circuit energizing the filaments of the tubes Hi2, I04- and N11: momentarily for each. revolution of the clutch member 29 During the times the switch. i3 is open, the. mechanism isinoperative, and. the plate relay 43. is deenergized. The

quick-heating filaments, so that by closing the switch 53 for a brief period of time, the circuit may be placed in operation.

If a vehicle is parked in the parking stall, the oscillator I02 will go into oscillation at each momentary energization and the output tube it! will be biased to cut oil. so that the relay 43 remains deenergized. However, should the parked vehicle be removed from the parking area, the next closing of the switch 53 will energize the filament circuits for the vacuum tubes without causing the oscillator I62 to go into oscillation. The resulting absence of a negative grid bias on the output tube I01 at the time that tube is energized will permit the tube to draw plate current and energize the relay 43 so as to complete the circuit to the resetting solenoid (H and reset the parking meter to zero.

It will be seen that, by making the open circuit time of the switch 53 long with respect to the closed circuit time, the life of the battery I I3 may be greatly prolonged. This also correspondingly prolongs the life of the plate battery II2 since no plate current is drawn by any of the vacuum tubes during the time their filament circuits are deenergized.

In Figure 6, there is illustrated an electronic control apparatus which responds to a change in the inductance of a pickup coil by varying the frequency of an alternating current generated by the apparatus. As is shown in Figure 6, the sensing unit I8 comprises a pickup coil 26 which. is tapped as is shown and connected as the tuning inductance of a conventional oscillator circuit employing an oscillator tube I2I. The coil I20 is shunted by a variable tuning condenser I22 through adjustment of which the frequency generated by the oscillator may be varied as desired.

A second oscillator of like construction but operating at a fixed frequency employs a vacuum tube I23 connected to a tuning coil I24 shunted by a fixed tuning condenser I25. The output of the oscillator I23 is mixed with the output of the oscillator I2I by connecting a tap on the coil I24 to the tap on the coil I26, as by means of conductor I26. The mixed outputs of the two oscillators HI and I23 are taken from the conductor I26 and applied to the primary winding I21 of a coupling transformer I28. The other terminal of the primary winding I21 is connected as indicated at I29 to a suitable source of plate supply potential which is applied to the anodes of the tubes I'2I and I23 through the transformer winding 12'! and through the tuning coils I20 and I24, respectively. A secondary winding I30 of the transformer I28 is connected through a rectifier 3! to a load resistance I32 so as to develop across the load resistance I32 a negative potential which is applied as indicated at I33 as a grid bias to an output tube I34. The plate relay 43 is connected in the anode circuit of the output tube I34.

The variable condenser I22 is adjusted with the parking area vacant to cause the oscillator I2I to generate a frequency which is substantially equal to the frequency generated by the oscillator 523. Under these conditions, the voltage developed across the rectifier load resistance I32 is of extremely low magnitudeand the tube I34 draws plate current so as to energize the plate relay 43. l-Iowever, when a vehicle is moved into the parking area, the effective inductance of the coil I20 is changed by reason of the large mass of magnetic material positioned near thereto. This change in inductance upsets the equality between the frequencies generated by the two oscillators so as to produce across the rectifier load resistance I32 a negative potential of sufllcient magnitude to bias the output tube I34 to cut oil and deenergize the relay 43. The relay 43 is 0peratively connected with the resetting solenoid 3I in a manner identical to that hereinbefore described.

In Figure 7, there is illustrated an alternative inductance-responsive circuit in which a change in the inductance of a pickup coil I50, resulting from the removal of a parked vehicle from the parking area, is used to change the balance conditions of an inductance bridge comprising a fixed inductance I5I and resistance legs I52 and I53. The two inductances I and I5I and the two resistances I52 and I53 are connected in a Wheatstone bridge circuit which is energized by alternating current at diagonally opposite corners of the bridge, as by means of power from a commercial source such as is represented by the terminals I54.

All or a portion of the resistance leg I53 is made variable so that the bridge may be balanced for the condition when no vehicle is in the parking stall. When the bridge is so balanced, the potential measured across the remaining diagonal of the bridge is substantially zero. The balance of the bridge will be upset by the parking of a vehicle in the stall so as to produce between these diagonally opposite corners an alternating current signal which is applied by means of conductors I55 and I56 to an input potentiometer I51. A movable tap on the potentiometer I51 is connected to apply a selected portion of the output signal to the primary winding l58 of an input transformer I59, the secondary 533 of which is connected by conventional circuit arrangements to a pentode amplifier tube I6 I. The amplified output signal appears across a plate load resistance I62 which may be coupled in a conventional fashion to the grid of a second amplifying tube I63. The second amplifying tube is transformer coupled, as indicated at I64, to the grid of a gas discharge tube I65. The plate relay 43 is connected in the anode circuit of the gas discharge tube I65.

The circuit shown in Figure 7 and just described operates in a manner opposite to that characterizing the circuits previously described in that the resetting of the parking meter results from a deenergization of the plate relay 43 as distinguished from operation following energization of the relay as is characteristic of the previously described circuits. It will be seen that, in the absence of a vehicle parked in the parking stall, the signal which is applied to the grid of the gas discharge tube I65 will be of negligibly small value with the result that the gas discharge tube will remain in its non-conductive condition and the relay 43 will be deenergized. When a vehicle is parked in the parking stall, the balance of thebridge is upset and a substantial signal is applied to the grid of the gas discharge tube I65, triggering the tube and causing the same to draw anodecurrent and energize the relay 43.

Because of the reversal of the operating characteristics, the resetting solenoid 3| is connected in circuit with the normally closed contacts of the relay 43 so as to be energized in response to deenergization of the relay 43 when a parked vehicle is removed from the parking area.

In Figure .9, a still further modified form of the invention is illustrated for sensing the presence or absence of a parked vehicle by the result- F3 l ng-changein'the inductanceoia pickup. coil; l 15-. 'I'he-piclup coil l His-connected as. shown: at: [1165 tptlie grid of-a'vacuum' tube [11 which,. in asso'-- elationa vacuum tube I318, isiconnected in a conventional multivibrator circuit. The circult constants are s selected: as; to; make: the: multivibrator' self-oscillating? when a. vehicle, is parkedi'rr the parking: stall.

Thepickuin coil IPi istshunted; by; a fixed' condenser I 19% and thei Q-"ofthis;circuit is changed suiflciently by theldepartureof. a vehicle from the parking area-mo cause the; multivibrator circuit to 'stop oscillating:

With this arrangement the oscillator EH. l:l-8\ generates an output-signal, onlyduring the presence oi: a veh-icle' in the: parking area. Thisv output signal is applied; as indicated at Iii-0;. to a vacuum tubeamplifier-["81 ;.and the amplified output signal is. applied}. as. indicated at I82; to a rectifier 183i serving to produce'acrossa load re-' slstance Ill-I a direct :potential which; by virtue of itscoupling to:th'e grid of a vacuum tube H35, serves to: control the operationv of the vacuum tube:- Asds characteristic of the systems hereinbefore described}. the: arrangement is such as to: cause the tube l85i to draw plate current and energize the relayi 435 connected" in" the anode cir-- cuit thereofwhen a. parked: vehicle is removed front the: parking area.

The circuit which is illustrated? in Figure 8' employs an sensing unit. 1'81, a multiturn iron cored pickup: c'oih 2011. The magnetic flux in-- duced in the iron" core Ofi the coil 200 by the earth's magnetic: field is'caused to change. ma'gnitude by the distortion of the" earths mag-- rret'ie field resulting from; the; movement of a vehicle intoor'out of the: parking area in which the sen'sing unit is placed; This changein magni tude of flux: induces a momentary potential: which i'samplified in: a high-gain, two-stage amplifi'er employing vacuum tubes- :2? and? 2103. The amplified-output is coupl'ed astby a: coupling. transformer" 2M to' a rectifier 205 which operates; to produce across a load. resistance 20.6 a biasing potentiaf which is applied; as indicated at 2 01 to. the grid of an output tube- 208. The. plate:- relay Wi's connected in anodecircuit'of the output tube 108i It will be recognized that the polarity of the momentary voltageapplied: to: the input of the amplifier 202-403 will depend upon whether) a vehicle is beingmoved into the parking area or being removed therefrom. The position of the coil 2W or the connections thereto are so adjustedv as tocause a negative potential to be developed across the rectifier load resistance 206 when'th'e vehicle is beihg'removed from the parkin g spa'ce soas to control'the output tube203 'and plate relay 43 in the same manner as has been hereinhefore described: When a vehicle is being'move'd into the parking space, the polarity of the. momentary voltage developed on conductor fml is' opposite to that just assumed, and accordi'ngly applies to" the'rectifier 2'05 asignal of opposi'te polarity. This, signal is of the wrong polarity to cause current't'o flow in the rectifier circuit, and the relay 431's therefore not responsi'verto movements of vehicles into parking position, and responds only to the removal of ve hicles. from the parking space.

In. the description of Figure 2', reference was made to a time delay means 42'. Such a time delay means is included in each of the circuits abovedescribed. In Figure 3; for example, the time delay is obtained by a condenser 2W con- I4 n rectedt in: shunt with. the:- cathode load: resistance: 1:-

Ilhet time: constant of the resistance. Fl: and? condenser 2:10; is made relatively long so; as: toe maintain: the; bias. voltage on. the grids of. the. output-1 tube: 1.5? for: an. appreciable length. of: time. after" the signah induced: inthe pickup coil; 624: falls; substantiallyto zero; As the condenser. 2:10 slowly discharges. through the plate load: re.- sistance' 121?, the. grid of thetube 19 gradually shifts. in: the. positive. direction, and eventually.- the tube 19 draws plate current of sufl'icient magnitude: to energize the relay 43'. By appropriate adziustment; of the electrical values." of: the resistance 11 and? condenser 2H), substan-.-' tially any desired time delaymay be obtained. Ordinarily, thisidel'ay should: be: of the order of magnitude of 'teni seconds to-insure that thezpa-rke ing meter isn'ot; reset untilthe vehicle is actually'removed from the.parking space,v thus avoidingv faulty operation; of the device due t0 mo? mentary changes in the coupling. between: the: excitor: coil 611 and. the. pickup coil 61.

Aswill be seen from. an inspection of thet'draw ings'; a similar'tim'e delay may be incorporated inta-each of thetci'rcuits' described herein by con-'- necting a condenser of suitable capacityin parallel with the: load resistance for each of the rectifiers;

In each of the various forms of: the. invention described herein; the. vacuum tube amplifiers; rectifi'ers; and output tubes: may be replaced by a conventional magnetic amplifier by using as the relay 43" a device which. is designed to operate on alternating current. Such. an arrang-ement isillustrated diagrammatically in. Figure 10'- whereinthe sensing unit I8 is shown as'connected' totheinput" of a magnetic amplifier 41, the output of which is connected to the relay- 4'3;

'I he magnetic amplifier 4'1"" may comprise'any eitheconventional variations of the well known: saturable reactor. For example, alternating current power maybe supplied to the amplifierfrom terminals 220-; and a controlled fraction of the. voltage-so applied is used tocontrol theoperatiorr ct theirelay- 43.- The output of the. sensing unit 1 8 servestocontrol the magnitude ofsuch. fraction by varying the degree of saturation of the. magnetic: core of the amplifier. Zero signal operati'ng levels are. established: by the direct current bias: supplied from. a. battery 22 through: a. variable: resistance. 222.

From the foregoing, it: will: be observed that this inventionprovides a parking meter which includes an electronicv apparatus operating. to. sensethe' departure of a vehicle from. the park-- i-ng area or stall associated with the parking meter; and operating in response. tosthat. deter minaticn' to reset the. parking meter'to zero. This; of'course', makes itnecessary for thenext motorist parking a vehicle in that parking. area to= insert theappropriate" coin in the parking meter even though a considerable amount of 'unexpired time would remain on the parking meter but for the automatic resetting thereof; It will be seen that by so resetting the parking meters whenever the parking stall is vacated, the amount of revenue which may be collected by the park'- ing meters can be substantially increased.

This invention embraces broadly the concept of sensing through electronic means whether the parking area associated with the parking meter occupi'emby a parked vehicle. In the various forms oftheinvention illustrated and described herein, there have been disclosed electronic sensing mechanisms responsive to changes in the mutual inductance between two related inductance coils, to changes in capacitance of an electrical circuit, to changes in inductance in an ini'nductance coil used to change the frequency of an alternating current or unbalance an inductance bridge circuit or change the Q of a tuned circuit, and to changes in the orientation of the earth magnetic field; all such changes resulting from the departure of a vehicle from the parking area.

Attention is directed particularly to the arrangement of a group of such parking meters in a parking meter system so as to indicate at a suitably located supervisory station any and all violations of the parking ordinances, as Well as indicating the total number of operations of the parking meters comprising the system.

It will also be noted from the foregoing that the apparatus of this invention obviates the difficulties attendant upon the necessity of winding the spring motors used in the timing mechanisms of parking meters. In the present invention, the winding of the spring motor is accomplished automatically upon each automatic resetting of the time indicator.

Attention is also directed to the use of the periodically operated momentary contact mechanism for repeatedly energizing the sensing apparatus for short periods of time so as to materially extend the life of batteries used in a battery powered installation.

While the preferred embodiments of each of the various aspects of thi invention have been illustrated and described herein, the invention is not to be limited to the details shown and described except as defined in the appended claims.

We claim:

1. In a parking meter, the combination of: a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time; timing means coacting with said indicator to move the same to said zero position upon expiration of said time, said timing means including a driving spring; resetting means operable upon actuation at any time to move said indicator to said zero position; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said resetting means and operably responsive to said signal for actuating said resetting means; a source of power for energizing said electrical means; intermittently operated switch means coupled to said timing means for operation thereby connected in circuit between said source and said electrical means for periodically momentarily energizing said electrical means; and time delay means coacting with said electrical means for delaying actuation of said resetting means until a predetermined time after production of said signal.

2. In a parking meter, the combination of: a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time; timing means coacting with said indicator for moving the same toward said zero position at a rate equal to the rate of expiration of said time, said timing means including a driving spring; resetting means operable upon actuation at any time to move said indicator to said zero postion; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said resetting means; rewind means connected to said timing means for winding said driving spring; and a connection between said rewind means and said resetting means; said electrical means being onerably responsive to said signal from said sensing means for simultaneously actuating said resetting means and said rewind means to return said time indicator to a zero position and rewind said driving spring.

3. A resetting control mechanism for parking meters according to claim 2 in which said sensing means comprises a pickup coil disposed in a position relatively adjacent to a vehicle parked in a given parking area, and an exciting coil disposed relatively adjacent to said pickup coil to induce therein a substantial alternating potential when a vehicle is parked in said given parking area, said exciting coil being so oriented with respect to said pickup coil as to provide minimum intercoupling therebetween in the absence of said vehicle; and in which said electrical means is responsive to a material reduction in said alternating potential induced in said pickup coil and resulting from the departure of said vehicle from said area.

4. A resetting control mechanism for parking meters according to claim 2 in which said sensing means comprises an inductance coil disposed in a position relatively adjacent to a vehicle parked in a given parking area, said coil having a given self-inductance when said vehicle is parked in said area, and a measurably different self-inductance when said vehicle is removed from said area; and in which said electrical means includes an oscillatory circuit containing said inductance coil for generating a control potential, said oscillatory circuit being responsive to a change in said self-inductance to produce a change in said control potential; and in which said electrical means also includes an actuating means responsive to said change in said control potential for actuating said power operated means upon the departure of said vehicle from said area.

5. A resetting control mechanism for parking meters according to claim 2 in which said sensing means comprises an inductance coil disposed in a position relatively adjacent to a vehicle parked in a given parking area, said coil having a given self-inductance when said vehicle is parked in said area, and a measurably different self-inductance when said vehicle is removed from said area; and in which said electrical means includes an oscillatory circuit for generating an alternating control potential and containing said inductance coil as a frequency determining element thereof, said oscillatory circuit being responsive to a change in said self-inductance to produce a change in the frequency of said control potential; and in which said electrical means also includes an actuating means responsive to said change in the frequency of said control potential for actuating saidpower operated means upon the departure of said vehicle from said area.

6. A resetting control mechanism for parking meters according to claim 2 in which said sensing means comprises an inductance coil disposed in a position relatively adjacent to a vehicle parked in a given parking area, said coil hav- 17 a given self-inductance when said vehicle is parked insaid area, and a measurably difierent sell-inductance when said vehicle is removed from said area; and in which said electrical means includes an inductance bridge circuit contalning said inductance coil; and in which said electrical mean-s also includes an actuating means responsive to changes in the balance of said bridge circuit for actuating said power operated means upon the departure of said vehicle from said area.

7. A resetting control mechanism for parking meters according to claim '2 in which said sensmeans immprises a pickup coil wound about a core of'magnetic material disposed in a position relatively adjacent to a vehicle parked in a given parking area; and in which said electrical means is responsive to a potential induced in said pickiipcoil and resulting from a change in the magnetic flux induced in said core by the earths magnetic field, said change resulting from the change in orientation of the earths magnetic field at the location of said pickup coil caused by the departure of said vehicle from said area.

8. A resetting control mechanism for parking meters according to claim 2 in which said electrical means includes a magnetic amplifier for amplifying said signal, and an actuating means responsive to the amplified signal for actuating said power operated means.

i 9. In a parking meter, the combination of a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time; timing means coacting with said indicator to move the same to said zero position upon expiration of said time; resetting means operable upon actuation at any time to move said indicator to said zero position; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said resetting means and operably responsive to said signal for actuating said resetting means; a source of power for energizing said electrical means; and intermittently operated switch means coupled to said timing means for operation thereby connected in circuit between said source and said electrical means for periodically momentarily energizing said electrical means.

10. In a parking meter, the combination of: a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time; timing means coacting with said indicator to move the same to said zero position upon expiration of said time; resetting means operable upon actuation at any time to move said indicator to :said zero position; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said resetting means and operably responsive to said signal for actuating said resetting means; and time delay means coacting with said electrical means for delaying actuation of said resetting means until a predetermined time after production of said signal.

11. In a resetting control mechanism for parking meters having a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time, and including timing means coacting with said indicator to move the same to said zero position upon expiration of said time, and said timing means including a driving spring, the combination of: power operated means operable upon actuation at any time to move said indicator to said zero position; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical neans connected between said sensing means and said power operated means and operably responsive to said signal for actuating said power operated means to thereby reset said time indicator to said zero position; means connected between said power operated means and said timing means for Winding said driving spring in response to actuation of said power operated means; a source of power for energizing said electrical means; intermittently operated switch means coupled to said timing means for operation thereby connected in circuit between said source and said electrical means for periodically momentarily energizing said electrical means; and time delay means coacting with said electrical means for delaying actuation of said power operated means until a predetermined time after production of said signal.

12. In a resetting control mechanism for park-. ing meters having a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time, and including timing means coacting with said indicator for moving the same toward said zero position at a rate equal to the rate of expiration of said time, and said timing means including a driving spring, the combination of power operated means operable upon actuation at any time to move said indicator to said zero position; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said power operated means; rewind means connected to said timing means for winding said driving spring; a connection between said rewind means and said power operated means; said electrical means being operably responsive to said signal from said sensing means for simultaneously actuating said power operated means and said rewind means to return said time indicator to a zero position and rewind said driving spring.

13. In a resetting control mechanism for parking meters having a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time, and including timing means coacting with said indicator to move the same to said zero position upon expiration of said time, the combination of: power operated means op-- erable upon actuation at any time to move said indicator to said Zero position; sensing means responsiVe to the presence of a vehicle in a given parking area for producing a, signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said power operated means and operably responsive to said signal for actuating said power operated means to thereby reset said time indicator to said zero position; a source of power for energizing said electrical means; and intermittently operated switch means coupled to said timing means for operation thereby connected in circuit between said source and said electrical means for periodically momentarily energizing said electrical means.

14. In a resetting control mechanism for parking meters having a time indicator movable from a zero position to an operative position in response to manually movable means for indicating unexpired time, and including timing means coacting with said indicator to move the same to said zero position upon expiration of said time, the combination of: power operated means operable upon actuation at any time to move said indicator to said zero position; sensing means responsive to the presence of a vehicle in a given parking area for producing a signal representing the departure of said vehicle from said area; electrical means connected between said sensing means and said power operated means and operably responsive to said signal for actuating said power operated means to thereby reset said time indicator to said zero position; and time deday means coacting with said electrical means for delaying actuation of said power operated means until a predetermined time after production of said signal.

DONALD G. GUMPERTZ. RUSSEL C. ALEXANDER.

, References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,950,741 Nein et a1. Mar. 13, 1934 2,074,443 Walpole Mar. 23, 1937 2,152,577 Weaver Mar. 28, 1939 2,178,315 Sweetla'nd Oct. 31, 1939 2,277,612 Symington Mar. 24, 1942 2,355,395 Rubenstein Aug. 8, 1944 2,386,942 Edelman Oct. 16, 1945 2,492,182 Robinson Dec. 27, 1949 2,623,933 Allstadt Dec. 30, 1952 

